Segment types as delimiters and addressable resource identifiers

ABSTRACT

An example device for processing media data is configured to parse a bitstream including the media data, the bitstream being formatted according to Common Media Application Format (CMAF), detect, during the parsing, a file type (FTYP) value for a CMAF track file of the bitstream, determine that a CMAF header of the CMAF track file starts with the FTYP value, and process one or more CMAF fragments following the CMAF header of the CMAF track file. The device may additionally be configured to detect one or more segment type (STYP) values in the bitstream, determine that each of the one or more STYP values corresponds to a start of a respective one of the CMAF fragments, and process each of the CMAF fragments starting from the corresponding STYP value.

This application claims the benefit of U.S. Provisional Application No.62/481,594, filed Apr. 4, 2017, the entire contents of which are herebyincorporated by reference.

TECHNICAL FIELD

This disclosure relates to storage and transport of media data.

BACKGROUND

Digital video capabilities can be incorporated into a wide range ofdevices, including digital televisions, digital direct broadcastsystems, wireless broadcast systems, personal digital assistants (PDAs),laptop or desktop computers, digital cameras, digital recording devices,digital media players, video gaming devices, video game consoles,cellular or satellite radio telephones, video teleconferencing devices,and the like. Digital video devices implement video compressiontechniques, such as those described in the standards defined by MPEG-2,MPEG-4, ITU-T H.263 or ITU-T H.264/MPEG-4, Part 10, Advanced VideoCoding (AVC), ITU-T H.265 (also referred to High Efficiency Video Coding(HEVC)), and extensions of such standards, to transmit and receivedigital video information more efficiently.

After media data has been encoded, the media data may be packetized fortransmission or storage. The media data may be assembled into a videofile conforming to any of a variety of standards, such as theInternational Organization for Standardization (ISO) base media fileformat and extensions thereof, such as AVC.

SUMMARY

In general, this disclosure describes techniques for using data types(e.g., segment types and/or file types) as delimiters, type indicators,and delivery indicators. These techniques may allow use of these datatypes in a flexible, simple fashion to provide any or all of theseindications. In this manner, generated content may be used in differentdelivery and/or consumption environments, but also allow for packagingas discussed in greater detail below.

In one example, a method of processing media data includes parsing, by aprocessor implemented in circuitry, a bitstream including data formattedaccording to Common Media Application Format (CMAF), detecting, by theprocessor and during the parsing, a file type (FTYP) value for a CMAFtrack file of the bitstream, determining, by the processor, that a CMAFheader of the CMAF track file starts with the FTYP value, andprocessing, by the processor, one or more CMAF fragments following theCMAF header of the CMAF track file.

In another example, a device for processing media data includes a memoryfor storing media data; and one or more processors implemented incircuitry and configured to: parse a bitstream including the media data,the bitstream being formatted according to Common Media ApplicationFormat (CMAF); detect, during the parsing, a file type (FTYP) value fora CMAF track file of the bitstream; determine that a CMAF header of theCMAF track file starts with the FTYP value; and process one or more CMAFfragments following the CMAF header of the CMAF track file.

In another example, a device for processing media data includes meansfor parsing a bitstream including data formatted according to CommonMedia Application Format (CMAF); means for detecting, during theparsing, a file type (FTYP) value for a CMAF track file of thebitstream; means for determining that a CMAF header of the CMAF trackfile starts with the FTYP value; and means for processing one or moreCMAF fragments following the CMAF header of the CMAF track file.

In another example, a computer-readable storage medium (which may benon-transitory) has stored thereon instructions that, when executed,cause a processor to parse a bitstream including data formattedaccording to Common Media Application Format (CMAF); detect, during theparsing, a file type (FTYP) value for a CMAF track file of thebitstream; determine that a CMAF header of the CMAF track file startswith the FTYP value; and process one or more CMAF fragments followingthe CMAF header of the CMAF track file.

In another example, a method of generating a bitstream including mediadata includes generating, by a processor implemented in circuitry, aCommon Media Application Format (CMAF) header of a CMAF track file;setting, by the processor, a value for a file type (FTYP) value of theCMAF header indicating the start of the CMAF header; encapsulating, bythe processor, one or more samples of media data in one or more CMAFfragments following the CMAF header of the CMAF track file; andgenerating, by the processor, a bitstream including the CMAF header andthe CMAF track file, the one or more CMAF fragments following the CMAFheader in the CMAF track file.

In another example, a device for generating a bitstream including mediadata includes a memory configured to store media data; and one or moreprocessors implemented in circuitry and configured to: generate, by aprocessor implemented in circuitry, a Common Media Application Format(CMAF) header of a CMAF track file for the media data; set a value for afile type (FTYP) value of the CMAF header indicating the start of theCMAF header; encapsulate one or more samples of the media data in one ormore CMAF fragments following the CMAF header of the CMAF track file;and generate a bitstream including the CMAF header and the CMAF trackfile, the one or more CMAF fragments following the CMAF header in theCMAF track file.

In another example, a device for generating a bitstream including mediadata includes means for generating a Common Media Application Format(CMAF) header of a CMAF track file; means for setting a value for a filetype (FTYP) value of the CMAF header indicating the start of the CMAFheader; means for encapsulating one or more samples of media data in oneor more CMAF fragments following the CMAF header of the CMAF track file;and means for generating a bitstream including the CMAF header and theCMAF track file, the one or more CMAF fragments following the CMAFheader in the CMAF track file.

In another example, a computer-readable storage medium (which may benon-transitory) has stored thereon instructions that, when executed,cause a processor to generate a Common Media Application Format (CMAF)header of a CMAF track file; set a value for a file type (FTYP) value ofthe CMAF header indicating the start of the CMAF header; encapsulate oneor more samples of media data in one or more CMAF fragments followingthe CMAF header of the CMAF track file; and generate a bitstreamincluding the CMAF header and the CMAF track file, the one or more CMAFfragments following the CMAF header in the CMAF track file.

The details of one or more examples are set forth in the accompanyingdrawings and the description below. Other features, objects, andadvantages will be apparent from the description and drawings, and fromthe claims.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a block diagram illustrating an example system that implementstechniques for streaming media data over a network.

FIG. 2 is a block diagram illustrating an example set of components ofthe retrieval unit of FIG. 1 in greater detail.

FIG. 3 is a conceptual diagram illustrating elements of examplemultimedia content.

FIG. 4 is a block diagram illustrating elements of an example videofile, which may correspond to a segment of a representation.

FIG. 5 is a conceptual diagram illustrating an example Common MediaApplication Format (CMAF) fragment.

FIG. 6 is a conceptual diagram illustrating an example CMAF track.

FIG. 7 is a conceptual diagram illustrating an example CMAF segment.

FIGS. 8A and 8B are conceptual diagrams illustrating example CMAFchunks.

FIG. 9 is a conceptual diagram illustrating an example system inaccordance with the techniques of this disclosure.

FIG. 10 is a conceptual diagram illustrating an example decompositionwithin a WAVE application using HTML-5 APIs between platform, content,and application, each of which may use data according to the techniquesof this disclosure.

FIG. 11 is a conceptual diagram illustrating an example box sequence andcontainment of a CMAF chunk.

FIG. 12 is a flowchart illustrating an example method of generating abitstream in accordance with the techniques of this disclosure.

FIG. 13 is a flowchart illustrating an example of a method of processingmedia data in accordance with the techniques of this disclosure.

DETAILED DESCRIPTION

In general, this disclosure describes techniques for using data types(e.g., segment types and/or file types) as delimiters, type indicators,and delivery indicators.

Dynamic Adaptive Streaming over HTTP (DASH) describes the use ofsegments as deliverable containers of media data (e.g., files withunique uniform resource locators (URLs)). Segments have a type,described by a “segment type” or “styp” syntax element. Files also havea file type, described by a “file type” or “ftyp” syntax element. Suchsyntax elements may form part of file format information according to,e.g., the ISO base media file format (ISO BMFF) or an extension of ISOBMFF.

A file conforming to ISO BMFF or an extension of ISO BMFF may furtherinclude media data formatted according to Common Media ApplicationFormat (CMAF). CMAF content is used in different stages: at the contentpreparation stage, at the delivery level, and at the content consumptionstage (e.g., for an interface to a receiving device, such as a mediasource extension (MSE) interface).

In general, CMAF data structures are identified without a manifest file,such as a DASH media presentation description (MPD). After contentpreparation, delimiters are typically included in byte streams/files toidentify the CMAF data structures. At the delivery level, types fordelivered objects should be identifiable. As interfaces to playbackengines, such as MSEs, data structures may be identified for extraction,e.g., to permit playback and switching across different CMAF tracks. Ingeneral, identification of CMAF data structures should be simple, andfollow the CMAF structure.

The techniques of this disclosure may be applied to video filesconforming to video data encapsulated according to any of ISO base mediafile format, Scalable Video Coding (SVC) file format, Advanced VideoCoding (AVC) file format, Third Generation Partnership Project (3GPP)file format, and/or Multiview Video Coding (MVC) file format, or othersimilar video file formats.

In HTTP streaming, frequently used operations include HEAD, GET, andpartial GET. The HEAD operation retrieves a header of a file associatedwith a given uniform resource locator (URL) or uniform resource name(URN), without retrieving a payload associated with the URL or URN. TheGET operation retrieves a whole file associated with a given URL or URN.The partial GET operation receives a byte range as an input parameterand retrieves a continuous number of bytes of a file, where the numberof bytes correspond to the received byte range. Thus, movie fragmentsmay be provided for HTTP streaming, because a partial GET operation canget one or more individual movie fragments. In a movie fragment, therecan be several track fragments of different tracks. In HTTP streaming, amedia presentation may be a structured collection of data that isaccessible to the client. The client may request and download media datainformation to present a streaming service to a user.

In the example of streaming 3GPP data using HTTP streaming, there may bemultiple representations for video and/or audio data of multimediacontent. As explained below, different representations may correspond todifferent coding characteristics (e.g., different profiles or levels ofa video coding standard), different coding standards or extensions ofcoding standards (such as multiview and/or scalable extensions), ordifferent bitrates. The manifest of such representations may be definedin a Media Presentation Description (MPD) data structure. A mediapresentation may correspond to a structured collection of data that isaccessible to an HTTP streaming client device. The HTTP streaming clientdevice may request and download media data information to present astreaming service to a user of the client device. A media presentationmay be described in the MPD data structure, which may include updates ofthe MPD.

A media presentation may contain a sequence of one or more Periods. Eachperiod may extend until the start of the next Period, or until the endof the media presentation, in the case of the last period. Each periodmay contain one or more representations for the same media content. Arepresentation may be one of a number of alternative encoded versions ofaudio, video, timed text, or other such data. The representations maydiffer by encoding types, e.g., by bitrate, resolution, and/or codec forvideo data and bitrate, language, and/or codec for audio data. The termrepresentation may be used to refer to a section of encoded audio orvideo data corresponding to a particular period of the multimediacontent and encoded in a particular way.

Representations of a particular period may be assigned to a groupindicated by an attribute in the MPD indicative of an adaptation set towhich the representations belong. Representations in the same adaptationset are generally considered alternatives to each other, in that aclient device can dynamically and seamlessly switch between theserepresentations, e.g., to perform bandwidth adaptation. For example,each representation of video data for a particular period may beassigned to the same adaptation set, such that any of therepresentations may be selected for decoding to present media data, suchas video data or audio data, of the multimedia content for thecorresponding period. The media content within one period may berepresented by either one representation from group 0, if present, orthe combination of at most one representation from each non-zero group,in some examples. Timing data for each representation of a period may beexpressed relative to the start time of the period.

A representation may include one or more segments. Each representationmay include an initialization segment, or each segment of arepresentation may be self-initializing. When present, theinitialization segment may contain initialization information foraccessing the representation. In general, the initialization segmentdoes not contain media data. A segment may be uniquely referenced by anidentifier, such as a uniform resource locator (URL), uniform resourcename (URN), or uniform resource identifier (URI). The MPD may providethe identifiers for each segment. In some examples, the MPD may alsoprovide byte ranges in the form of a range attribute, which maycorrespond to the data for a segment within a file accessible by theURL, URN, or URI.

Different representations may be selected for substantially simultaneousretrieval for different types of media data. For example, a clientdevice may select an audio representation, a video representation, and atimed text representation from which to retrieve segments. In someexamples, the client device may select particular adaptation sets forperforming bandwidth adaptation. That is, the client device may selectan adaptation set including video representations, an adaptation setincluding audio representations, and/or an adaptation set includingtimed text. Alternatively, the client device may select adaptation setsfor certain types of media (e.g., video), and directly selectrepresentations for other types of media (e.g., audio and/or timedtext).

FIG. 1 is a block diagram illustrating an example system 10 thatimplements techniques for streaming media data over a network. In thisexample, system 10 includes content preparation device 20, server device60, and client device 40. Client device 40 and server device 60 arecommunicatively coupled by network 74, which may comprise the Internet.In some examples, content preparation device 20 and server device 60 mayalso be coupled by network 74 or another network, or may be directlycommunicatively coupled. In some examples, content preparation device 20and server device 60 may comprise the same device.

Content preparation device 20, in the example of FIG. 1, comprises audiosource 22 and video source 24. Audio source 22 may comprise, forexample, a microphone that produces electrical signals representative ofcaptured audio data to be encoded by audio encoder 26. Alternatively,audio source 22 may comprise a storage medium storing previouslyrecorded audio data, an audio data generator such as a computerizedsynthesizer, or any other source of audio data. Video source 24 maycomprise a video camera that produces video data to be encoded by videoencoder 28, a storage medium encoded with previously recorded videodata, a video data generation unit such as a computer graphics source,or any other source of video data. Content preparation device 20 is notnecessarily communicatively coupled to server device 60 in all examples,but may store multimedia content to a separate medium that is read byserver device 60.

Raw audio and video data may comprise analog or digital data. Analogdata may be digitized before being encoded by audio encoder 26 and/orvideo encoder 28. Audio source 22 may obtain audio data from a speakingparticipant while the speaking participant is speaking, and video source24 may simultaneously obtain video data of the speaking participant. Inother examples, audio source 22 may comprise a computer-readable storagemedium comprising stored audio data, and video source 24 may comprise acomputer-readable storage medium comprising stored video data. In thismanner, the techniques described in this disclosure may be applied tolive, streaming, real-time audio and video data or to archived,pre-recorded audio and video data.

Audio frames that correspond to video frames are generally audio framescontaining audio data that was captured (or generated) by audio source22 contemporaneously with video data captured (or generated) by videosource 24 that is contained within the video frames. For example, whilea speaking participant generally produces audio data by speaking, audiosource 22 captures the audio data, and video source 24 captures videodata of the speaking participant at the same time, that is, while audiosource 22 is capturing the audio data. Hence, an audio frame maytemporally correspond to one or more particular video frames.Accordingly, an audio frame corresponding to a video frame generallycorresponds to a situation in which audio data and video data werecaptured at the same time and for which an audio frame and a video framecomprise, respectively, the audio data and the video data that wascaptured at the same time.

In some examples, audio encoder 26 may encode a timestamp in eachencoded audio frame that represents a time at which the audio data forthe encoded audio frame was recorded, and similarly, video encoder 28may encode a timestamp in each encoded video frame that represents atime at which the video data for encoded video frame was recorded. Insuch examples, an audio frame corresponding to a video frame maycomprise an audio frame comprising a timestamp and a video framecomprising the same timestamp. Content preparation device 20 may includean internal clock from which audio encoder 26 and/or video encoder 28may generate the timestamps, or that audio source 22 and video source 24may use to associate audio and video data, respectively, with atimestamp.

In some examples, audio source 22 may send data to audio encoder 26corresponding to a time at which audio data was recorded, and videosource 24 may send data to video encoder 28 corresponding to a time atwhich video data was recorded. In some examples, audio encoder 26 mayencode a sequence identifier in encoded audio data to indicate arelative temporal ordering of encoded audio data but without necessarilyindicating an absolute time at which the audio data was recorded, andsimilarly, video encoder 28 may also use sequence identifiers toindicate a relative temporal ordering of encoded video data. Similarly,in some examples, a sequence identifier may be mapped or otherwisecorrelated with a timestamp.

Audio encoder 26 generally produces a stream of encoded audio data,while video encoder 28 produces a stream of encoded video data. Eachindividual stream of data (whether audio or video) may be referred to asan elementary stream. An elementary stream is a single, digitally coded(possibly compressed) component of a representation. For example, thecoded video or audio part of the representation can be an elementarystream. An elementary stream may be converted into a packetizedelementary stream (PES) before being encapsulated within a video file.Within the same representation, a stream ID may be used to distinguishthe PES-packets belonging to one elementary stream from the other. Thebasic unit of data of an elementary stream is a packetized elementarystream (PES) packet. Thus, coded video data generally corresponds toelementary video streams. Similarly, audio data corresponds to one ormore respective elementary streams.

Many video coding standards, such as ITU-T H.264/AVC and the upcomingHigh Efficiency Video Coding (HEVC) standard, define the syntax,semantics, and decoding process for error-free bitstreams, any of whichconform to a certain profile or level. Video coding standards typicallydo not specify the encoder, but the encoder is tasked with guaranteeingthat the generated bitstreams are standard-compliant for a decoder. Inthe context of video coding standards, a “profile” corresponds to asubset of algorithms, features, or tools and constraints that apply tothem. As defined by the H.264 standard, for example, a “profile” is asubset of the entire bitstream syntax that is specified by the H.264standard. A “level” corresponds to the limitations of the decoderresource consumption, such as, for example, decoder memory andcomputation, which are related to the resolution of the pictures, bitrate, and block processing rate. A profile may be signaled with aprofile idc (profile indicator) value, while a level may be signaledwith a level idc (level indicator) value.

The H.264 standard, for example, recognizes that, within the boundsimposed by the syntax of a given profile, it is still possible torequire a large variation in the performance of encoders and decodersdepending upon the values taken by syntax elements in the bitstream suchas the specified size of the decoded pictures. The H.264 standardfurther recognizes that, in many applications, it is neither practicalnor economical to implement a decoder capable of dealing with allhypothetical uses of the syntax within a particular profile.Accordingly, the H.264 standard defines a “level” as a specified set ofconstraints imposed on values of the syntax elements in the bitstream.These constraints may be simple limits on values. Alternatively, theseconstraints may take the form of constraints on arithmetic combinationsof values (e.g., picture width multiplied by picture height multipliedby number of pictures decoded per second). The H.264 standard furtherprovides that individual implementations may support a different levelfor each supported profile.

A decoder conforming to a profile ordinarily supports all the featuresdefined in the profile. For example, as a coding feature, B-picturecoding is not supported in the baseline profile of H.264/AVC but issupported in other profiles of H.264/AVC. A decoder conforming to alevel should be capable of decoding any bitstream that does not requireresources beyond the limitations defined in the level. Definitions ofprofiles and levels may be helpful for interpretability. For example,during video transmission, a pair of profile and level definitions maybe negotiated and agreed for a whole transmission session. Morespecifically, in H.264/AVC, a level may define limitations on the numberof macroblocks that need to be processed, decoded picture buffer (DPB)size, coded picture buffer (CPB) size, vertical motion vector range,maximum number of motion vectors per two consecutive MBs, and whether aB-block can have sub-macroblock partitions less than 8×8 pixels. In thismanner, a decoder may determine whether the decoder is capable ofproperly decoding the bitstream.

In the example of FIG. 1, encapsulation unit 30 of content preparationdevice 20 receives elementary streams comprising coded video data fromvideo encoder 28 and elementary streams comprising coded audio data fromaudio encoder 26. In some examples, video encoder 28 and audio encoder26 may each include packetizers for forming PES packets from encodeddata. In other examples, video encoder 28 and audio encoder 26 may eachinterface with respective packetizers for forming PES packets fromencoded data. In still other examples, encapsulation unit 30 may includepacketizers for forming PES packets from encoded audio and video data.

Video encoder 28 may encode video data of multimedia content in avariety of ways, to produce different representations of the multimediacontent at various bitrates and with various characteristics, such aspixel resolutions, frame rates, conformance to various coding standards,conformance to various profiles and/or levels of profiles for variouscoding standards, representations having one or multiple views (e.g.,for two-dimensional or three-dimensional playback), or other suchcharacteristics. A representation, as used in this disclosure, maycomprise one of audio data, video data, text data (e.g., for closedcaptions), or other such data. The representation may include anelementary stream, such as an audio elementary stream or a videoelementary stream. Each PES packet may include a stream_id thatidentifies the elementary stream to which the PES packet belongs.Encapsulation unit 30 is responsible for assembling elementary streamsinto video files (e.g., segments) of various representations.

Encapsulation unit 30 receives PES packets for elementary streams of arepresentation from audio encoder 26 and video encoder 28 and formscorresponding network abstraction layer (NAL) units from the PESpackets. Coded video segments may be organized into NAL units, whichprovide a “network-friendly” video representation addressingapplications such as video telephony, storage, broadcast, or streaming.NAL units can be categorized to Video Coding Layer (VCL) NAL units andnon-VCL NAL units. VCL units may contain the core compression engine andmay include block, macroblock, and/or slice level data. Other NAL unitsmay be non-VCL NAL units. In some examples, a coded picture in one timeinstance, normally presented as a primary coded picture, may becontained in an access unit, which may include one or more NAL units.

Non-VCL NAL units may include parameter set NAL units and SEI NAL units,among others. Parameter sets may contain sequence-level headerinformation (in sequence parameter sets (SPS)) and the infrequentlychanging picture-level header information (in picture parameter sets(PPS)). With parameter sets (e.g., PPS and SPS), infrequently changinginformation need not to be repeated for each sequence or picture, hencecoding efficiency may be improved. Furthermore, the use of parametersets may enable out-of-band transmission of the important headerinformation, avoiding the need for redundant transmissions for errorresilience. In out-of-band transmission examples, parameter set NALunits may be transmitted on a different channel than other NAL units,such as SEI NAL units.

Supplemental Enhancement Information (SEI) may contain information thatis not necessary for decoding the coded pictures samples from VCL NALunits, but may assist in processes related to decoding, display, errorresilience, and other purposes. SEI messages may be contained in non-VCLNAL units. SEI messages are the normative part of some standardspecifications, and thus are not always mandatory for standard compliantdecoder implementation. SEI messages may be sequence level SEI messagesor picture level SEI messages. Some sequence level information may becontained in SEI messages, such as scalability information SEI messagesin the example of SVC and view scalability information SEI messages inMVC. These example SEI messages may convey information on, e.g.,extraction of operation points and characteristics of the operationpoints. In addition, encapsulation unit 30 may form a manifest file,such as a media presentation descriptor (MPD) that describescharacteristics of the representations. Encapsulation unit 30 may formatthe MPD according to extensible markup language (XML).

Encapsulation unit 30 may provide data for one or more representationsof multimedia content, along with the manifest file (e.g., the MPD) tooutput interface 32. Output interface 32 may comprise a networkinterface or an interface for writing to a storage medium, such as auniversal serial bus (USB) interface, a CD or DVD writer or burner, aninterface to magnetic or flash storage media, or other interfaces forstoring or transmitting media data. Encapsulation unit 30 may providedata of each of the representations of multimedia content to outputinterface 32, which may send the data to server device 60 via networktransmission or storage media. In the example of FIG. 1, server device60 includes storage medium 62 that stores various multimedia contents64, each including a respective manifest file 66 and one or morerepresentations 68A-68N (representations 68). In some examples, outputinterface 32 may also send data directly to network 74.

In some examples, representations 68 may be separated into adaptationsets. That is, various subsets of representations 68 may includerespective common sets of characteristics, such as codec, profile andlevel, resolution, number of views, file format for segments, text typeinformation that may identify a language or other characteristics oftext to be displayed with the representation and/or audio data to bedecoded and presented, e.g., by speakers, camera angle information thatmay describe a camera angle or real-world camera perspective of a scenefor representations in the adaptation set, rating information thatdescribes content suitability for particular audiences, or the like.

Manifest file 66 may include data indicative of the subsets ofrepresentations 68 corresponding to particular adaptation sets, as wellas common characteristics for the adaptation sets. Manifest file 66 mayalso include data representative of individual characteristics, such asbitrates, for individual representations of adaptation sets. In thismanner, an adaptation set may provide for simplified network bandwidthadaptation. Representations in an adaptation set may be indicated usingchild elements of an adaptation set element of manifest file 66.

Server device 60 includes request processing unit 70 and networkinterface 72. In some examples, server device 60 may include a pluralityof network interfaces. Furthermore, any or all of the features of serverdevice 60 may be implemented on other devices of a content deliverynetwork, such as routers, bridges, proxy devices, switches, or otherdevices. In some examples, intermediate devices of a content deliverynetwork may cache data of multimedia content 64, and include componentsthat conform substantially to those of server device 60. In general,network interface 72 is configured to send and receive data via network74.

Request processing unit 70 is configured to receive network requestsfrom client devices, such as client device 40, for data of storagemedium 62. For example, request processing unit 70 may implementhypertext transfer protocol (HTTP) version 1.1, as described in RFC2616, “Hypertext Transfer Protocol—HTTP/1.1,” by R. Fielding et al,Network Working Group, IETF, June 1999. That is, request processing unit70 may be configured to receive HTTP GET or partial GET requests andprovide data of multimedia content 64 in response to the requests. Therequests may specify a segment of one of representations 68, e.g., usinga URL of the segment. In some examples, the requests may also specifyone or more byte ranges of the segment, thus comprising partial GETrequests. Request processing unit 70 may further be configured toservice HTTP HEAD requests to provide header data of a segment of one ofrepresentations 68. In any case, request processing unit 70 may beconfigured to process the requests to provide requested data to arequesting device, such as client device 40.

Additionally or alternatively, request processing unit 70 may beconfigured to deliver media data via a broadcast or multicast protocol,such as eMBMS. Content preparation device 20 may create DASH segmentsand/or sub-segments in substantially the same way as described, butserver device 60 may deliver these segments or sub-segments using eMBMSor another broadcast or multicast network transport protocol. Forexample, request processing unit 70 may be configured to receive amulticast group join request from client device 40. That is, serverdevice 60 may advertise an Internet protocol (IP) address associatedwith a multicast group to client devices, including client device 40,associated with particular media content (e.g., a broadcast of a liveevent). Client device 40, in turn, may submit a request to join themulticast group. This request may be propagated throughout network 74,e.g., routers making up network 74, such that the routers are caused todirect traffic destined for the IP address associated with the multicastgroup to subscribing client devices, such as client device 40.

As illustrated in the example of FIG. 1, multimedia content 64 includesmanifest file 66, which may correspond to a media presentationdescription (MPD). Manifest file 66 may contain descriptions ofdifferent alternative representations 68 (e.g., video services withdifferent qualities) and the description may include, e.g., codecinformation, a profile value, a level value, a bitrate, and otherdescriptive characteristics of representations 68. Client device 40 mayretrieve the MPD of a media presentation to determine how to accesssegments of representations 68.

In particular, retrieval unit 52 may retrieve configuration data (notshown) of client device 40 to determine decoding capabilities of videodecoder 48 and rendering capabilities of video output 44. Theconfiguration data may also include any or all of a language preferenceselected by a user of client device 40, one or more camera perspectivescorresponding to depth preferences set by the user of client device 40,and/or a rating preference selected by the user of client device 40.Retrieval unit 52 may comprise, for example, a web browser or a mediaclient configured to submit HTTP GET and partial GET requests. Retrievalunit 52 may correspond to software instructions executed by one or moreprocessors or processing units (not shown) of client device 40. In someexamples, all or portions of the functionality described with respect toretrieval unit 52 may be implemented in hardware, or a combination ofhardware, software, and/or firmware, where requisite hardware may beprovided to execute instructions for software or firmware.

Retrieval unit 52 may compare the decoding and rendering capabilities ofclient device 40 to characteristics of representations 68 indicated byinformation of manifest file 66. Retrieval unit 52 may initiallyretrieve at least a portion of manifest file 66 to determinecharacteristics of representations 68. For example, retrieval unit 52may request a portion of manifest file 66 that describes characteristicsof one or more adaptation sets. Retrieval unit 52 may select a subset ofrepresentations 68 (e.g., an adaptation set) having characteristics thatcan be satisfied by the coding and rendering capabilities of clientdevice 40. Retrieval unit 52 may then determine bitrates forrepresentations in the adaptation set, determine a currently availableamount of network bandwidth, and retrieve segments from one of therepresentations having a bitrate that can be satisfied by the networkbandwidth.

In general, higher bitrate representations may yield higher qualityvideo playback, while lower bitrate representations may providesufficient quality video playback when available network bandwidthdecreases. Accordingly, when available network bandwidth is relativelyhigh, retrieval unit 52 may retrieve data from relatively high bitraterepresentations, whereas when available network bandwidth is low,retrieval unit 52 may retrieve data from relatively low bitraterepresentations. In this manner, client device 40 may stream multimediadata over network 74 while also adapting to changing network bandwidthavailability of network 74.

Additionally or alternatively, retrieval unit 52 may be configured toreceive data in accordance with a broadcast or multicast networkprotocol, such as eMBMS or IP multicast. In such examples, retrievalunit 52 may submit a request to join a multicast network groupassociated with particular media content. After joining the multicastgroup, retrieval unit 52 may receive data of the multicast group withoutfurther requests issued to server device 60 or content preparationdevice 20. Retrieval unit 52 may submit a request to leave the multicastgroup when data of the multicast group is no longer needed, e.g., tostop playback or to change channels to a different multicast group.

Network interface 54 may receive and provide data of segments of aselected representation to retrieval unit 52, which may in turn providethe segments to decapsulation unit 50. Decapsulation unit 50 maydecapsulate elements of a video file into constituent PES streams,depacketize the PES streams to retrieve encoded data, and send theencoded data to either audio decoder 46 or video decoder 48, dependingon whether the encoded data is part of an audio or video stream, e.g.,as indicated by PES packet headers of the stream. Audio decoder 46decodes encoded audio data and sends the decoded audio data to audiooutput 42, while video decoder 48 decodes encoded video data and sendsthe decoded video data, which may include a plurality of views of astream, to video output 44.

Video encoder 28, video decoder 48, audio encoder 26, audio decoder 46,encapsulation unit 30, retrieval unit 52, and decapsulation unit 50 eachmay be implemented as any of a variety of suitable processing circuitry,as applicable, such as one or more microprocessors, digital signalprocessors (DSPs), application specific integrated circuits (ASICs),field programmable gate arrays (FPGAs), discrete logic circuitry,software, hardware, firmware or any combinations thereof. Each of videoencoder 28 and video decoder 48 may be included in one or more encodersor decoders, either of which may be integrated as part of a combinedvideo encoder/decoder (CODEC). Likewise, each of audio encoder 26 andaudio decoder 46 may be included in one or more encoders or decoders,either of which may be integrated as part of a combined CODEC. Anapparatus including video encoder 28, video decoder 48, audio encoder26, audio decoder 46, encapsulation unit 30, retrieval unit 52, and/ordecapsulation unit 50 may comprise an integrated circuit, amicroprocessor, and/or a wireless communication device, such as acellular telephone.

Client device 40, server device 60, and/or content preparation device 20may be configured to operate in accordance with the techniques of thisdisclosure. For purposes of example, this disclosure describes thesetechniques with respect to client device 40 and server device 60.However, it should be understood that content preparation device 20 maybe configured to perform these techniques, instead of (or in additionto) server device 60.

Encapsulation unit 30 may form NAL units comprising a header thatidentifies a program to which the NAL unit belongs, as well as apayload, e.g., audio data, video data, or data that describes thetransport or program stream to which the NAL unit corresponds. Forexample, in H.264/AVC, a NAL unit includes a 1-byte header and a payloadof varying size. A NAL unit including video data in its payload maycomprise various granularity levels of video data. For example, a NALunit may comprise a block of video data, a plurality of blocks, a sliceof video data, or an entire picture of video data. Encapsulation unit 30may receive encoded video data from video encoder 28 in the form of PESpackets of elementary streams. Encapsulation unit 30 may associate eachelementary stream with a corresponding program.

Encapsulation unit 30 may also assemble access units from a plurality ofNAL units. In general, an access unit may comprise one or more NAL unitsfor representing a frame of video data, as well audio data correspondingto the frame when such audio data is available. An access unit generallyincludes all NAL units for one output time instance, e.g., all audio andvideo data for one time instance. For example, if each view has a framerate of 20 frames per second (fps), then each time instance maycorrespond to a time interval of 0.05 seconds. During this timeinterval, the specific frames for all views of the same access unit (thesame time instance) may be rendered simultaneously. In one example, anaccess unit may comprise a coded picture in one time instance, which maybe presented as a primary coded picture.

Accordingly, an access unit may comprise all audio and video frames of acommon temporal instance, e.g., all views corresponding to time X Thisdisclosure also refers to an encoded picture of a particular view as a“view component.” That is, a view component may comprise an encodedpicture (or frame) for a particular view at a particular time.Accordingly, an access unit may be defined as comprising all viewcomponents of a common temporal instance. The decoding order of accessunits need not necessarily be the same as the output or display order.

A media presentation may include a media presentation description (MPD),which may contain descriptions of different alternative representations(e.g., video services with different qualities) and the description mayinclude, e.g., codec information, a profile value, and a level value. AnMPD is one example of a manifest file, such as manifest file 66. Clientdevice 40 may retrieve the MPD of a media presentation to determine howto access movie fragments of various presentations. Movie fragments maybe located in movie fragment boxes (moof boxes) of video files.

Manifest file 66 (which may comprise, for example, an MPD) may advertiseavailability of segments of representations 68. That is, the MPD mayinclude information indicating the wall-clock time at which a firstsegment of one of representations 68 becomes available, as well asinformation indicating the durations of segments within representations68. In this manner, retrieval unit 52 of client device 40 may determinewhen each segment is available, based on the starting time as well asthe durations of the segments preceding a particular segment.

After encapsulation unit 30 has assembled NAL units and/or access unitsinto a video file based on received data, encapsulation unit 30 passesthe video file to output interface 32 for output. In some examples,encapsulation unit 30 may store the video file locally or send the videofile to a remote server via output interface 32, rather than sending thevideo file directly to client device 40. Output interface 32 maycomprise, for example, a transmitter, a transceiver, a device forwriting data to a computer-readable medium such as, for example, anoptical drive, a magnetic media drive (e.g., floppy drive), a universalserial bus (USB) port, a network interface, or other output interface.Output interface 32 outputs the video file to a computer-readablemedium, such as, for example, a transmission signal, a magnetic medium,an optical medium, a memory, a flash drive, or other computer-readablemedium.

Network interface 54 may receive a NAL unit or access unit via network74 and provide the NAL unit or access unit to decapsulation unit 50, viaretrieval unit 52. Decapsulation unit 50 may decapsulate a elements of avideo file into constituent PES streams, depacketize the PES streams toretrieve encoded data, and send the encoded data to either audio decoder46 or video decoder 48, depending on whether the encoded data is part ofan audio or video stream, e.g., as indicated by PES packet headers ofthe stream. Audio decoder 46 decodes encoded audio data and sends thedecoded audio data to audio output 42, while video decoder 48 decodesencoded video data and sends the decoded video data, which may include aplurality of views of a stream, to video output 44.

In accordance with the techniques of this disclosure, encapsulation unit30 may use a single type of signaling for a variety of purposes, e.g.,any or all of a content preparation stage, delivery level, and/or acontent consumption stage. Likewise, retrieval unit 52 may use thissingle type of signaling for any or all of these purposes.

In one example, the single type of signaling is a file type (ftyp) boxthat includes a value acting as an identifier for one or more CMAFtracks. Thus, encapsulation unit 30 may set a value for the ftyp box,and retrieval unit 52 may read a value for the ftyp box. Additionally,request processing unit 70 may also read the value for the ftyp box.These components may use the value of the ftyp box during any or all ofcontent preparation, delivery, and/or content consumption.

Additionally or alternatively, the single type of signaling may be asegment type (styp) box that includes a value acting as an identifierfor one or more CMAF tracks. The styp box may act as a delimiter toidentify boundaries of CMAF fragments and/or chunks, identifiers forCMAF data structures, identifiers for DASH segments (or segments forother network streaming technologies), and/or as identifiers forprocessing requirements. Thus, encapsulation unit 30 may specify valuesfor one or more styp boxes of a segment to represent any or all ofboundaries of CMAF fragments and/or chunks of the segment, identifiersfor CMAF data structures of the segment, an identifier for the DASHsegment, and/or as identifiers for processing requirements for mediadata of the segment. In general, styp boxes are optional and may or maynot be used, to avoid issues with backward-compatibility and overhead.

Table 1 below represents example “brands” of type values in accordancewith the techniques of this disclosure, including locations of eachbrand type and example conformance requirements:

TABLE 1 Brand Location Conformance Requirements ′cmfc′ FileTypeBox andThe Common Media Application Track SegmentTypeBox Format ′cmfs′SegmentTypeBox CMAF Segments ′cmfl′ SegmentTypeBox CMAF Chunks ′cmff′SegmentTypeBox CMAF Fragment (identifies the presence the first samplesof the CMAF Fragment)

Tables 2-6 below represent additional example data structures that maybe used in accordance with the techniques of this disclosure:

TABLE 2 CMAF Track File Format NL 0 Req. Specification RequirementsDescription CMAF 1 CMAF CMAF 7.2 CMAF Header Header sidx 0/1 SegmentIndex CMAF All of CMAF CMAF CMAF Fragments Fragment CMAF Track

TABLE 3 CMAF Header Format CMAF NL 0 Req. ISOBMFF ConstraintsDescription ftyp 1 [ISOBMFF] CMAF 7.2 File Type and 4.3 Compatibilitycmfc moov 1 [ISOBMFF] Container for 8.2.1 functional metadata

TABLE 4 CMAF Segment Format NL 0 Req. Specification RequirementsDescription styp 0/1 [ISOBMFF] Segment Type 8.16.2 Signallingcompatibility to CMAF Segment cmfs CMAF 1+ CMAF 7.3.2.3 CMAF FragmentFragment

TABLE 5 CMAF Fragment Format NL 0 Req. Specification RequirementsDescription styp 0/1 [ISOBMFF] Segment Type 8.16.2 Signallingcompatibility to CMAF Fragment cmff CMAF 1+ CMAF Just above CMAF ChunkChunk

TABLE 6 CMAF Chunk Format NL 0 Req. Specification RequirementsDescription styp 0/1 [ISOBMFF] Segment Type 8.16.2 Signalingcompatibility to CMAF Chunk cmfl prft 0/1 [ISOBMFF] Producer Reference8.16.5 Time emsg * [DASH] CMAF Event Message 7.4.5 moof 1 [ISOBMFF]Movie Fragment 8.8.4 mdat 1 [ISOBMFF] CMAF Media Data container 8.2.27.5.18 for media samples

With respect to delivery and consumption, in some examples, ftyp andstyp provide indications of the compatibility of the type and how thetype can be used. The box may be at the start of the object, andtherefore, easy to find and parse (e.g., by retrieval unit 52 and/ordecapsulation unit 50). Multiple compatibility types may be used tosignal different types. The type of the box may also be exposed as anInternet Media type using the profiles parameter and, for example, beused in the HTTP case (e.g., for DASH streaming or other HTTP streamingtechnologies). This may enable different distribution modes.

With respect to use of types as delimiters, the type values may delimitchunks in fragments, delimit fragments in segments and track files,and/or delimit ranges to provide proper interpretation. The delimiter(e.g., type value) may also represent types, in order for a receivingelement (e.g., retrieval unit 52 and/or decapsulation unit 50) todetermine the type of data (e.g., media data) included in the chunk,fragment, segment, track file, or the like. No indices of subsequentfields are necessary, and hence, these techniques may support real-timeprocessing.

FIG. 2 is a block diagram illustrating an example set of components ofretrieval unit 52 of FIG. 1 in greater detail. In this example,retrieval unit 52 includes eMBMS middleware unit 100, DASH client 110,and media application 112.

In the example of FIG. 2, eMBMS middleware unit 100 further includeseMBMS reception unit 106, cache 104, and server unit 102. In thisexample, eMBMS reception unit 106 is configured to receive data viaeMBMS, e.g., according to File Delivery over Unidirectional Transport(FLUTE), described in T. Paila et al., “FLUTE—File Delivery overUnidirectional Transport,” Network Working Group, RFC 6726, Nov. 2012,available at http://tools.ietf.org/html/rfc6726. That is, eMBMSreception unit 106 may receive files via broadcast from, e.g., serverdevice 60, which may act as a BM-SC.

As eMBMS middleware unit 100 receives data for files, eMBMS middlewareunit may store the received data in cache 104. Cache 104 may comprise acomputer-readable storage medium, such as flash memory, a hard disk,RAM, or any other suitable storage medium.

Local server unit 102 may act as a server for DASH client 110. Forexample, local server unit 102 may provide a MPD file or other manifestfile to DASH client 110. Local server unit 102 may advertiseavailability times for segments in the MPD file, as well as hyperlinksfrom which the segments can be retrieved. These hyperlinks may include alocalhost address prefix corresponding to client device 40 (e.g.,127.0.0.1 for IPv4). In this manner, DASH client 110 may requestsegments from local server unit 102 using HTTP GET or partial GETrequests. For example, for a segment available from linkhttp://127.0.0.1/rep1/seg3, DASH client 110 may construct an HTTP GETrequest that includes a request for http://127.0.0.1/rep1/seg3, andsubmit the request to local server unit 102. Local server unit 102 mayretrieve requested data from cache 104 and provide the data to DASHclient 110 in response to such requests.

FIG. 3 is a conceptual diagram illustrating elements of examplemultimedia content 120. Multimedia content 120 may correspond tomultimedia content 64 (FIG. 1), or another multimedia content stored instorage medium 62. In the example of FIG. 3, multimedia content 120includes media presentation description (MPD) 122 and a plurality ofrepresentations 124A-124N (representations 124). Representation 124Aincludes optional header data 126 and segments 128A-128N (segments 128),while representation 124N includes optional header data 130 and segments132A-132N (segments 132). The letter N is used to designate the lastmovie fragment in each of representations 124 as a matter ofconvenience. In some examples, there may be different numbers of moviefragments between representations 124.

MPD 122 may comprise a data structure separate from representations 124.MPD 122 may correspond to manifest file 66 of FIG. 1. Likewise,representations 124 may correspond to representations 68 of FIG. 2. Ingeneral, MPD 122 may include data that generally describescharacteristics of representations 124, such as coding and renderingcharacteristics, adaptation sets, a profile to which MPD 122corresponds, text type information, camera angle information, ratinginformation, trick mode information (e.g., information indicative ofrepresentations that include temporal sub-sequences), and/or informationfor retrieving remote periods (e.g., for targeted advertisementinsertion into media content during playback).

Header data 126, when present, may describe characteristics of segments128, e.g., temporal locations of random access points (RAPs, alsoreferred to as stream access points (SAPs)), which of segments 128includes random access points, byte offsets to random access pointswithin segments 128, uniform resource locators (URLs) of segments 128,or other aspects of segments 128. Header data 130, when present, maydescribe similar characteristics for segments 132. Additionally oralternatively, such characteristics may be fully included within MPD122.

Segments 128, 132 include one or more coded video samples, each of whichmay include frames or slices of video data. Each of the coded videosamples of segments 128 may have similar characteristics, e.g., height,width, and bandwidth requirements. Such characteristics may be describedby data of MPD 122, though such data is not illustrated in the exampleof FIG. 3. MPD 122 may include characteristics as described by the 3GPPSpecification, with the addition of any or all of the signaledinformation described in this disclosure.

Each of segments 128, 132 may be associated with a unique uniformresource locator (URL). Thus, each of segments 128, 132 may beindependently retrievable using a streaming network protocol, such asDASH. In this manner, a destination device, such as client device 40,may use an HTTP GET request to retrieve segments 128 or 132. In someexamples, client device 40 may use HTTP partial GET requests to retrievespecific byte ranges of segments 128 or 132.

FIG. 4 is a block diagram illustrating elements of an example video file150, which may correspond to a segment of a representation, such as oneof segments 114, 124 of FIG. 3. Each of segments 128, 132 may includedata that conforms substantially to the arrangement of data illustratedin the example of FIG. 4. Video file 150 may be said to encapsulate asegment. As described above, video files in accordance with the ISO basemedia file format and extensions thereof store data in a series ofobjects, referred to as “boxes.” In the example of FIG. 4, video file150 includes file type (FTYP) box 152, movie (MOOV) box 154, segmentindex (sidx) boxes 162, movie fragment (MOOF) boxes 164, and moviefragment random access (MFRA) box 166. Although FIG. 4 represents anexample of a video file, it should be understood that other media filesmay include other types of media data (e.g., audio data, timed textdata, or the like) that is structured similarly to the data of videofile 150, in accordance with the ISO base media file format and itsextensions.

File type (FTYP) box 152 generally describes a file type for video file150. File type box 152 may include data that identifies a specificationthat describes a best use for video file 150. File type box 152 mayalternatively be placed before MOOV box 154, movie fragment boxes 164,and/or MFRA box 166.

In some examples, a Segment, such as video file 150, may include an MPDupdate box (not shown) before FTYP box 152. The MPD update box mayinclude information indicating that an MPD corresponding to arepresentation including video file 150 is to be updated, along withinformation for updating the MPD. For example, the MPD update box mayprovide a URI or URL for a resource to be used to update the MPD. Asanother example, the MPD update box may include data for updating theMPD. In some examples, the MPD update box may immediately follow asegment type (STYP) box (not shown) of video file 150, where the STYPbox may define a segment type for video file 150. FIG. 7, discussed ingreater detail below, provides additional information with respect tothe MPD update box.

MOOV box 154, in the example of FIG. 4, includes movie header (MVHD) box156, track (TRAK) box 158, and one or more movie extends (MVEX) boxes160. In general, MVHD box 156 may describe general characteristics ofvideo file 150. For example, MVHD box 156 may include data thatdescribes when video file 150 was originally created, when video file150 was last modified, a timescale for video file 150, a duration ofplayback for video file 150, or other data that generally describesvideo file 150.

TRAK box 158 may include data for a track of video file 150. TRAK box158 may include a track header (TKHD) box that describes characteristicsof the track corresponding to TRAK box 158. In some examples, TRAK box158 may include coded video pictures, while in other examples, the codedvideo pictures of the track may be included in movie fragments 164,which may be referenced by data of TRAK box 158 and/or sidx boxes 162.

In some examples, video file 150 may include more than one track.Accordingly, MOOV box 154 may include a number of TRAK boxes equal tothe number of tracks in video file 150. TRAK box 158 may describecharacteristics of a corresponding track of video file 150. For example,TRAK box 158 may describe temporal and/or spatial information for thecorresponding track. A TRAK box similar to TRAK box 158 of MOOV box 154may describe characteristics of a parameter set track, whenencapsulation unit 30 (FIG. 3) includes a parameter set track in a videofile, such as video file 150. Encapsulation unit 30 may signal thepresence of sequence level SEI messages in the parameter set trackwithin the TRAK box describing the parameter set track.

MVEX boxes 160 may describe characteristics of corresponding moviefragments 164, e.g., to signal that video file 150 includes moviefragments 164, in addition to video data included within MOOV box 154,if any. In the context of streaming video data, coded video pictures maybe included in movie fragments 164 rather than in MOOV box 154.Accordingly, all coded video samples may be included in movie fragments164, rather than in MOOV box 154.

MOOV box 154 may include a number of MVEX boxes 160 equal to the numberof movie fragments 164 in video file 150. Each of MVEX boxes 160 maydescribe characteristics of a corresponding one of movie fragments 164.For example, each MVEX box may include a movie extends header box (MEHD)box that describes a temporal duration for the corresponding one ofmovie fragments 164.

As noted above, encapsulation unit 30 may store a sequence data set in avideo sample that does not include actual coded video data. A videosample may generally correspond to an access unit, which is arepresentation of a coded picture at a specific time instance. In thecontext of AVC, the coded picture include one or more VCL NAL unitswhich contains the information to construct all the pixels of the accessunit and other associated non-VCL NAL units, such as SEI messages.Accordingly, encapsulation unit 30 may include a sequence data set,which may include sequence level SEI messages, in one of movie fragments164. Encapsulation unit 30 may further signal the presence of a sequencedata set and/or sequence level SEI messages as being present in one ofmovie fragments 164 within the one of MVEX boxes 160 corresponding tothe one of movie fragments 164.

SIDX boxes 162 are optional elements of video file 150. That is, videofiles conforming to the 3GPP file format, or other such file formats, donot necessarily include SIDX boxes 162. In accordance with the exampleof the 3GPP file format, a SIDX box may be used to identify asub-segment of a segment (e.g., a segment contained within video file150). The 3GPP file format defines a sub-segment as “a self-containedset of one or more consecutive movie fragment boxes with correspondingMedia Data box(es) and a Media Data Box containing data referenced by aMovie Fragment Box must follow that Movie Fragment box and precede thenext Movie Fragment box containing information about the same track.”The 3GPP file format also indicates that a SIDX box “contains a sequenceof references to subsegments of the (sub)segment documented by the box.The referenced subsegments are contiguous in presentation time.Similarly, the bytes referred to by a Segment Index box are alwayscontiguous within the segment. The referenced size gives the count ofthe number of bytes in the material referenced.”

SIDX boxes 162 generally provide information representative of one ormore sub-segments of a segment included in video file 150. For instance,such information may include playback times at which sub-segments beginand/or end, byte offsets for the sub-segments, whether the sub-segmentsinclude (e.g., start with) a stream access point (SAP), a type for theSAP (e.g., whether the SAP is an instantaneous decoder refresh (IDR)picture, a clean random access (CRA) picture, a broken link access (BLA)picture, or the like), a position of the SAP (in terms of playback timeand/or byte offset) in the sub-segment, and the like.

Movie fragments 164 may include one or more coded video pictures. Insome examples, movie fragments 164 may include one or more groups ofpictures (GOPs), each of which may include a number of coded videopictures, e.g., frames or pictures. In addition, as described above,movie fragments 164 may include sequence data sets in some examples.Each of movie fragments 164 may include a movie fragment header box(MFHD, not shown in FIG. 4). The MFHD box may describe characteristicsof the corresponding movie fragment, such as a sequence number for themovie fragment. Movie fragments 164 may be included in order of sequencenumber in video file 150. In some examples, one or more of moviefragments 164 may be preceded by a CMAF header, e.g., in accordance withTable 3 as discussed above. Moreover, a CMAF segment may include one ormore CMAF fragments, each of which may include one or more optionalboxes, a movie fragment box, and a media data box.

MFRA box 166 may describe random access points within movie fragments164 of video file 150. This may assist with performing trick modes, suchas performing seeks to particular temporal locations (i.e., playbacktimes) within a segment encapsulated by video file 150. MFRA box 166 isgenerally optional and need not be included in video files, in someexamples. Likewise, a client device, such as client device 40, does notnecessarily need to reference MFRA box 166 to correctly decode anddisplay video data of video file 150. MFRA box 166 may include a numberof track fragment random access (TFRA) boxes (not shown) equal to thenumber of tracks of video file 150, or in some examples, equal to thenumber of media tracks (e.g., non-hint tracks) of video file 150.

In some examples, movie fragments 164 may include one or more streamaccess points (SAPs), such as IDR pictures. Likewise, MFRA box 166 mayprovide indications of locations within video file 150 of the SAPs.Accordingly, a temporal sub-sequence of video file 150 may be formedfrom SAPs of video file 150. The temporal sub-sequence may also includeother pictures, such as P-frames and/or B-frames that depend from SAPs.Frames and/or slices of the temporal sub-sequence may be arranged withinthe segments such that frames/slices of the temporal sub-sequence thatdepend on other frames/slices of the sub-sequence can be properlydecoded. For example, in the hierarchical arrangement of data, data usedfor prediction for other data may also be included in the temporalsub-sequence.

FIG. 5 is a conceptual diagram illustrating an example CMAF fragment200. CMAF fragment 200 of FIG. 5 may correspond to one of moviefragments 164 of FIG. 4. CMAF fragment 200 may conform to Table 5 above.CMAF fragments, such as CMAF fragment 200, may be the smallest switchingunits that are handled by CMAF encoding, CMAF delivery, and CMAFplayers.

In the example of FIG. 5, CMAF fragment 200 includes zero or moreoptional boxes 202, a movie fragment (moof) box 204, and a media data(mdat) box 206. Optional boxes 202 are outlined with a dashed line toindicate that optional boxes 202 are optional. Optional boxes 202 ofFIG. 5 may include none, any, or all of a segment type box, a producerreference time box, and/or DASH event message box(es).

MDAT box 206 includes random access media samples 208A-208C (randomaccess media samples 208), which may correspond to one or more codedvideo streams (CVSs). A decode time 210 of a first sample, e.g., anordinal first sample, of MDAT box 206 (e.g., random access media sample208A) may be indicated by a track fragment decode time (tfdt) box, whichmay be included in moof box 204. In particular, the tfdt box may beinclude in a track fragment (traf) box of moof box 204, and may indicatea track fragment base media decode time.

In some examples, CMAF fragments, such as CMAF fragment 200, conform tothe following constraints:

-   -   1. Each CMAF Fragment, in combination with its associated CMAF        Header, shall contain sufficient metadata to be decoded,        decrypted, and displayed when it is independently accessed. In        addition to specified CMAF Track and Media Profile constraints,        a CMAF Track is non-conformant if a CMAF Fragment cannot be        decoded when processed with its associated CMAF Header. For        instance, if sample groups and sample group descriptions are        used to signal encryption key changes, then a        SampleGroupDescriptionBox and SampleToGroupBox needs to be        present in the TrackFragmentBox to make the CMAF Fragment        randomly accessible and decryptable.    -   2. The CMAF Fragment MovieFragmentBox may be preceded by other        boxes, including one or more SegmentTypeBox,        ProducerReferenceTimeBox and/or DASHEventMessageBox(es). (See        7.4.5 and Annex E. of ISO/IEC 23000-19 for more information on        Event Messages).    -   3. Each CMAF Fragment in a CMAF Track should have a duration of        at least one second, with the possible exception of the first        and last Fragments of the Track.

FIG. 6 is a conceptual diagram illustrating an example CMAF track 220.In this example, CMAF track 220 includes CMAF header 222 and CMAFfragments 230A, 230B (CMAF fragments 230). Each of CMAF fragments 230includes a respective set of zero or more optional boxes, a moof box,and an mdat box. For example, CMAF fragment 230A includes optional boxes224A, moof box 226A, and mdat box 228A, while CMAF fragment 230Bincludes optional boxes 224B, moof box 226B, and mdat box 228B. In thismanner, each of CMAF fragments 230 may generally include elementssimilar to the elements of CMAF fragment 200 of FIG. 5. CMAF track 220of FIG. 6 may be included within a video file, such as video file 150 ofFIG. 4, where CMAF header 222 may correspond to ftyp box 152 and moovbox 154 of FIG. 4, and CMAF fragments 230 may begin at the beginning ofmovie fragments 164 of FIG. 4. CMAF track 200 may generally conform toTable 2 above.

According to the techniques of this disclosure, CMAF header 222 mayinclude an ftyp value at NL 0, as discussed above, and as shown in theexample of Table 3. That is, content preparation device 20 of FIG. 1 mayset the ftyp value, at least in part, to indicate the start of CMAFheader 222. Likewise, client device 40 of FIG. 1 (e.g., retrieval unit52 of FIG. 1) may determine the location of CMAF header 222 by parsing abitstream including CMAF track 220 and detecting the ftyp value. Inresponse, retrieval unit 52 may determine that CMAF fragments 230 followCMAF header 222 (e.g., ftyp box 152 and moov box 154 of FIG. 4),potentially also after one or more intervening sidx boxes, such as sidxboxes 162 (FIG. 4).

Moreover, each of CMAF fragments 230 may include styp valuesrepresentative of whether the CMAF fragments 230 correspond to CMAFfragments only, CMAF segments, or CMAF chunks, e.g., in correspondingmoof boxes 226A, 226B (moof boxes 226). Thus, retrieval unit 52 maydetermine whether one of CMAF fragments 230 is a CMAF fragment only, aCMAF chunk, or a CMAF segment, according to the values for the styp ofthe respective CMAF fragments in the respective moof boxes 226.

For example, content preparation device 20 (FIG. 1) may assign a valueof “cmfl” to the styp element of one of moof boxes 226 of acorresponding one of CMAF fragments 230 to indicate that the one of CMAFfragments 230 includes a CMAF chunk, a value of “cmff” to indicate thatthe one of CMAF fragments 230 is a CMAF fragment only, or a value of“cmfs” to indicate that the one of CMAF fragments 230 is included in aCMAF segment. Likewise, retrieval unit 52 may determine that one of CMAFfragments 230 includes a CMAF chunk when an styp element of the one ofmoof boxes 226 has a value of “cmfl,” that the CMAF fragment is only aCMAF fragment when the styp element of the one of moof boxes 226 has avalue of “cmff,” or that the CMAF fragment is included in a CMAF segmentwhen the styp element of the one of moof boxes 226 has a value of“cmfs.”

FIG. 7 is a conceptual diagram illustrating an example CMAF segment 240.CMAF segment 240 of FIG. 7 may be included within a CMAF track file,following a CMAF header, e.g., as shown in FIG. 6. CMAF segment 240 mayconform to Table 4 above.

In the example of FIG. 7, CMAF segment 240 includes two example CMAFfragments 250A, 250B (CMAF fragments 250). Each of CMAF fragments 250includes a respective set of zero or more optional boxes, a moof box,and an mdat box. For example, CMAF fragment 250A includes optional boxes244A, moof box 246A, and mdat box 248A, while CMAF fragment 250Bincludes optional boxes 244B, moof box 246B, and mdat box 248B. In thismanner, each of CMAF fragments 250 may generally include elementssimilar to the elements of CMAF fragment 200 of FIG. 5. CMAF segment 240of FIG. 7 may be included within a video file, such as video file 150 ofFIG. 4, where CMAF fragments 250 may begin at the beginning of moviefragments 164 of FIG. 4.

In accordance with the techniques of this disclosure, contentpreparation device 20 (FIG. 1) may assign a value of “cmfs” to an stypvalue of moof box 246A of CMAF fragment 250A to indicate that CMAFfragment 250A is included within and represents the start of CMAFsegment 240. Likewise, retrieval unit 52 of FIG. 1 may determine thatCMAF fragment 250A represents the start of CMAF segment 240 in responseto determining that an styp value of moof box 246A of CMAF fragment 250Ahas a value of “cmfs.”

FIGS. 8A and 8B are conceptual diagrams illustrating example CMAFfragments and CMAF chunks. In particular, FIG. 8A illustrates an exampleof a CMAF fragment 260 only. That is, CMAF fragment 260 includes moofbox 262, mdat box 264, and coded video sequence samples 266A-266L (codedvideo sequence samples 266). FIG. 8B illustrates an example of a CMAFfragment 270 including CMAF chunks 272A-272D (CMAF chunks 272). Each ofCMAF chunks 272 may conform to Table 6 above. That is, in this example,each of CMAF chunks 272 includes a respective moof box 274A-274D (moofboxes 274), mdat boxes 276A-276D (mdat boxes 276), and respective codedvideo sequence samples 278A-278L (coded video sequence samples 276).

CMAF chunks 272, as shown, may be included within CMAF fragment 270,which may be included within CMAF tracks and/or CMAF segments, asdiscussed above. In one example, CMAF chunks are the smallest atomicunits that are handled by CMAF encoding, CMAF delivery, and CMAFPlayers. By dividing CMAF fragment 270 into CMAF chunks 272, e.g., asshown in FIG. 8B, media data of coded video sequence samples 278 can beoutput more frequently than media data of coded video sequence samples266 of FIG. 8A. That is, content preparation device 20 of FIG. 1, forexample, may output each of CMAF chunks 272 at respective encoder outputtimes 280A-280D (encoder output times 280). By contrast, contentpreparation device 20 may output the entire CMAF fragment 260 at encoderoutput time 268. In this manner, using CMAF chunks, such as CMAF chunks272, may reduce latency of transporting media data for a streamingservice.

CMAF chunks 272 may be labeled as having styp values of “cmfl” inrespective moof boxes 274, per the techniques of this disclosure. Thatis, content preparation device 20 may specify the value of “cmfl” in therespective moof boxes 274. Likewise, retrieval unit 52 may determinethat CMAF fragment 270 includes CMAF chunks 272 based on the value of“cmfl” in the respective moof boxes 274. Retrieval unit 52 may alsodetermine the start of each of CMAF chunks 272 by parsing CMAF fragment270 and detecting the value of “cmfl” for styp values of the respectivemoof boxes 274.

In some examples, CMAF chunks may conform to the following constraints:

-   -   1. A CMAF Fragment shall include one or more ISO Base Media        segments [ISOBMFF, 8.16] that each contains one        MovieFragmentBox, followed by one or more MediaDataBox(es)        containing the samples it references.    -   2. A CMAF fragment shall contain a MovieFragmentHeaderBox        constrained as specified in 7.5.14 of ISO/IEC 23000-19.    -   3. Each TrackFragmentBox shall contain one TrackFragmentB        aseMediaDecodeTimeBox.    -   4. All media samples in a CMAF Fragment shall be addressed by        byte offsets in the TrackRunBox that are relative to the first        byte of the MovieFragmentBox (see [ISOBMFF] 8.8.4).    -   5. The CMAF Chunk MovieFragmentBox may be preceded by other        boxes, including a SegmentTypeBox, one or more        ProducerReferenceTimeBox and/or DASHEventMessageBox(es). (See        7.4.5 and Annex E. for more information on Event Messages).

FIG. 9 is a conceptual diagram illustrating an example system 300 inaccordance with the techniques of this disclosure. In this example,system 300 is divided into four logical portions: a manifest portion, acontent offering portion, a delivery portion, and a platforms andplayers portion. The manifest portion and the content offering portionmay generally correspond to content preparation device 20 of FIG. 1, thedelivery portion may correspond to server device 60 of FIG. 1, and theplatforms and players portion may correspond to client device 40 of FIG.1.

In the example of FIG. 9, the manifest portion of system 300 includesDASH MPD 302, HTTP live streaming (HLS) M3U8 playlist 304, and anapplication 306. DASH MPD 302 references CMAF content 308, which isincluded in the content offering portion of system 300. CMAF content 308is provided to a content delivery network (CDN) 310, which providesbroadcast and/or multicast services as part of the delivery portion ofsystem 300. Various platforms and players of the platforms and playersportion of system 300 may receive media data from CDN 310, such as astand-alone HTTP live streaming (HLS) player 312, a device 314 forreceiving HLS as an HTML-5 video tag, a stand-alone DASH player 316, adevice 318 for receiving DASH as an HTML-5 video tag, and/or an HTML-5MSE-based Type-3 player 320. The techniques of this disclosure maygenerally support one type of signaling for devices configured accordingto any or all of these example use cases.

FIG. 10 is a conceptual diagram illustrating an example decomposition330 within a WAVE application 336 using HTML-5 application programminginterfaces (APIs) 338 between platform 332, content 334, and application336, each of which may use data according to the techniques of thisdisclosure. WAVE device platform 334 may have a set of capabilities thatare accessible for application 336 through HTML-5 APIs 338 and detailedcodec capabilities. WAVE content 332 may be played on WAVE deviceplatform 334 within WAVE application 336. WAVE application 336 may usethe capabilities of WAVE platform device 334 for media services.

FIG. 11 is a conceptual diagram illustrating an example box sequence andcontainment of a CMAF chunk 350. In this example, lower boxes indicatecontainment in the box above. That is, CMAF chunk includes segment type(‘styp’) box 352, producer reference time (‘prft’) event (‘emsg’) 354,movie fragment (‘moof’) box 356, and media data (‘mdat’) box. Moof box356, in turn, includes movie fragment header (‘mfhd’) box 360,protection specific header (‘pssh’) box 362, and track fragment Oran box364. The sequence of boxes contained in the traf box 364 as shown inFIG. 11 is one example. In this example, traf box 364 includes trackfragment header (‘tfhd’) box 370, track fragment run (‘trun’) box 372,sample encryption (‘senc’) box 374, sample auxiliary information sizes(‘saiz’) box 376, sample auxiliary information offsets (‘saio’) box 378,sample to group (‘sbgp’) box 380, and sample group descriptions (‘sgpd’)box 382. Boxes shown with dashed outlines, such as styp box 352, prtfemsg 354, and pssh box 362, may be optional. Certain boxes of traf box364 as shown in the bottom row are conditionally required whenencryption is used, in some examples.

In one example, any CMAF Chunk or CMAF Fragment that contains theinitial samples of a CMAF Fragment are to conform to the CMAF Segmentbrand ‘cmff’ and the brand should be signaled in the ‘styp.’

CMAF Headers, CMAF Fragments, and CMAF Chunks may be packaged andreferenced as CMAF Addressable Media Objects for storage and delivery,as described in Section 6.7 of the CMAF Media Object Model. Each CMAFAddressable Media Object may be referenced as a Resource by an externalspecification, e.g. MPEG DASH.

The CMAF Header, CMAF Chunks and CMAF Fragments may be made available asCMAF Addressable Resources by simple transformation means, for example:

-   -   Directly,    -   By concatenating CMAF Fragments and sending as CMAF Segment,        and/or    -   By concatenating CMAF Header with all CMAF Fragments, possibly        adding a SegmentIndexBox.

In CMAF fragment mode, a CMAF header may be available as an addressableobject. In this mode, the CMAF Fragment may be directly made availableas a CMAF Addressable Media Object.

In CMAF segment mode, CMAF segments may be used as discussed above,e.g., with respect to Table 4 and FIG. 7. A CMAF segment may be definedas a CMAF Addressable Media Object that contains one or more completeCMAF Fragments in presentation order. In some examples:

-   -   1. A CMAF Segment may contain the Samples of each CMAF Fragment        divided into multiple movie fragments sequenced in decode order.    -   2. A CMAF Segment may include a SegmentTypeBox preceding the        first MovieFragmentBox of each CMAF Fragment. The SegmentTypeBox        MAY include the CMAF Segment brand ‘cmfs’, and any compatible        brands listed in the FileTypeBox of the CMAF Track's CMAF        Header.

In CMAF chunk mode, the CMAF Header may be available an addressableobject. Each CMAF Fragment, in this mode, may be included in one or moreCMAF Chunks. The CMAF Chunk may be directly made available as a CMAFAddressable Media Object. The initial CMAF may include two CMAF Segmentbrands, ‘cmff and cmfl’, to signal the compatibility to the initial partof the CMAF Fragment as well as to the CMAF chunk. Non-initial CMAFChunks may include the CMAF Segment brand ‘cmfl’ to signal thecompatibility to this segment format.

A CMAF track file may be a CMAF Addressable Media Object defined to be aCMAF Track stored as a single track in an ISO BMFF file, with the firstCMAF Fragment baseMediaDecodeTime equal to zero. The CMAF Header and allCMAF Fragments may be included in a single CMAF Track File. In someexamples, a CMAF track file conforms to the following constraints:

-   -   1. Additional boxes, such as SegmentIndexBoxes, may be present        between the CMAF Header and the first CMAF Fragment.    -   2. If SegmentIndexBoxes exist, each subsegment referenced in the        SegmentIndexBox shall be a single CMAF Fragment contained in the        CMAF Track File.    -   3. Emsg and prtf boxes contained in CMAF Fragments are        maintained in the track file. If an emsg or prtf is maintained        for a CMAF Fragment, then the SegmentIndexBox shall reference        the start of the CMAF fragment, i.e., the earlier of prtf or any        emsg.    -   4. A video CMAF Track File may contain an offset edit list to        adjust the earliest presentation time of the first presented        sample to baseMediaDecodeTime of zero by subtracting any        composition delay added by the use of a v0 TrackRunBox using        positive composition offset values to reorder video frames from        decode order to presentation order. See 7.5.12 of ISO/IEC        23000-19.    -   5. A v1 TrackRunBox using negative composition offsets MAY be        used to adjust the composition time of the earliest presented        video Sample in each CMAF Fragment to its BaseMediaDecodeTime,        and the earliest video Sample in the CMAF Track File to zero,        without using an offset edit list.

FIG. 12 is a flowchart illustrating an example method of generating abitstream in accordance with the techniques of this disclosure. Themethod of FIG. 12 is explained with respect to content preparationdevice 20 (FIG. 1). However, it should be understood that other devicesmay be configured to perform this or a similar method. For example,server device 60 may perform some or all steps of the method of FIG. 12.

Initially, audio encoder 26 and video encoder 28 (FIG. 1) encode mediadata, such as audio or video data respectively, to form encoded samplesof media data. Encapsulation unit 30 (FIG. 1) then receives the encodedsamples of media data and generates a bitstream including the encodedsamples formatted according to CMAF in accordance with the techniques ofthis disclosure. In particular, encapsulation unit 30 generates a CMAFheader of a CMAF track file (400). Encapsulation unit 30 may generatethe CMAF header according to Table 3 above. For example, encapsulationunit 30 may set a file type (ftyp) value of the CMAF header at the startof the CMAF header (402). Encapsulation unit 30 may also generate amovie (moov) box of the CMAF header, e.g., including the elements ofmoov box 154 of FIG. 4.

Encapsulation unit 30 may then encapsulate the encoded media samples inrespective CMAF fragments (404). In various examples, the CMAF fragmentsmay correspond to CMAF fragments only, CMAF fragments included in CMAFsegments, or CMAF fragments including CMAF chunks. Accordingly,encapsulation unit 30 may set segment type (styp) values at the start ofthe CMAF fragments, to indicate starts of the CMAF fragments and typesfor the CMAF fragments (e.g., CMAF fragments only, CMAF segments, orCMAF chunks). As noted above, the value “cmfs” may represent a CMAFsegment, the value “cmff” may represent a CMAF fragment only, and thevalue “cmfl” may represent a CMAF chunk. Encapsulation unit 30 may setthe styp values in respective moof boxes of the CMAF fragments.

Encapsulation unit 30 may then generate a bitstream (408) including theCMAF header and CMAF fragments, and send the bitstream to a clientdevice (410), such as client device 40 (FIG. 1). In some examples,content preparation device 20 may send the bitstream to server device60, which may then send the bitstream to client device 40.

In this manner, the method of FIG. 12 represents an example of a methodof generating a bitstream, the method including generating, by aprocessor implemented in circuitry, a Common Media Application Format(CMAF) header of a CMAF track file; setting, by the processor, a valuefor a file type (FTYP) value of the CMAF header indicating the start ofthe CMAF header; encapsulating, by the processor, one or more samples ofmedia data in one or more CMAF fragments following the CMAF header ofthe CMAF track file; and generating, by the processor, a bitstreamincluding the CMAF header and the CMAF track file, the one or more CMAFfragments following the CMAF header in the CMAF track file.

FIG. 13 is a flowchart illustrating an example of a method of processingmedia data in accordance with the techniques of this disclosure. Themethod of FIG. 13 is explained with respect to client device 40 ofFIG. 1. However, it should be understood that other devices may beconfigured to perform this or a similar method in accordance with thetechniques of this disclosure.

Initially, retrieval unit 52 (FIG. 1) of client device 40 parses abitstream including a CMAF track file (420). It should be understoodthat retrieval unit 52 may initially request the bitstream from, e.g.,server device 60 or content preparation device 20 (FIG. 1). Whileparsing the bitstream, retrieval unit 52 may detect a file type (ftyp)value of the CMAF track file (422). As shown in Table 3 above, the ftypvalue may be at the start of a CMAF header of the CMAF track file.Accordingly, retrieval unit 52 may determine that the CMAF header startswith the ftyp value (424). Retrieval unit 52 may further determine thatthe rest of the CMAF header (e.g., a moov box) follows the ftyp value.

Retrieval unit 52 may, therefore, determine that one or more CMAFfragments of the CMAF track file follow the CMAF header (and any sidxboxes, if present, e.g., as shown in Table 2 above and in FIG. 4). Inparticular, retrieval unit 52 may continue parsing the bitstreamfollowing the CMAF header and detect one or more segment type (styp)values following the CMAF header (426). Retrieval unit 52 may detect thestyp values in respective moof boxes of the CMAF fragments. Inaccordance with the techniques of this disclosure, retrieval unit 52 maydetermine that each of the styp values represents the start of acorresponding CMAF fragment. Moreover, retrieval unit 52 may determinetypes for the CMAF fragments from the respective styp values. Asdiscussed above, in some examples, the value “cmfs” for styp mayrepresent a CMAF segment, the value “cmff” for styp may represent a CMAFfragment only, and the value “cmfl” for styp may represent a CMAF chunk.

Therefore, retrieval unit 52 may process the corresponding CMAFfragments starting at the respective styp values according to the stypvalues (428). For example, retrieval unit 52 may determine whether aCMAF fragment only follows the styp value, whether one or more CMAFfragments are to be expected as part of a CMAF segment (e.g., as shownin FIG. 7), or whether the CMAF fragment includes one or more CMAFchunks (e.g., as shown in FIG. 8B).

In this manner, the method of FIG. 13 represents an example of a methodof processing media data, the method including parsing, by a processorimplemented in circuitry, a bitstream including data formatted accordingto Common Media Application Format (CMAF), detecting, by the processorand during the parsing, a file type (FTYP) value for a CMAF track fileof the bitstream, determining, by the processor, that a CMAF header ofthe CMAF track file starts with the FTYP value, and processing, by theprocessor, one or more CMAF fragments following the CMAF header of theCMAF track file.

In one or more examples, the functions described may be implemented inhardware, software, firmware, or any combination thereof. If implementedin software, the functions may be stored on or transmitted over as oneor more instructions or code on a computer-readable medium and executedby a hardware-based processing unit. Computer-readable media may includecomputer-readable storage media, which corresponds to a tangible mediumsuch as data storage media, or communication media including any mediumthat facilitates transfer of a computer program from one place toanother, e.g., according to a communication protocol. In this manner,computer-readable media generally may correspond to (1) tangiblecomputer-readable storage media which is non-transitory or (2) acommunication medium such as a signal or carrier wave. Data storagemedia may be any available media that can be accessed by one or morecomputers or one or more processors to retrieve instructions, code,and/or data structures for implementation of the techniques described inthis disclosure. A computer program product may include acomputer-readable medium.

By way of example, and not limitation, such computer-readable storagemedia can comprise RAM, ROM, EEPROM, CD-ROM or other optical diskstorage, magnetic disk storage, or other magnetic storage devices, flashmemory, or any other medium that can be used to store desired programcode in the form of instructions or data structures and that can beaccessed by a computer. Also, any connection is properly termed acomputer-readable medium. For example, if instructions are transmittedfrom a website, server, or other remote source using a coaxial cable,fiber optic cable, twisted pair, digital subscriber line (DSL), orwireless technologies such as infrared, radio, and microwave, then thecoaxial cable, fiber optic cable, twisted pair, DSL, or wirelesstechnologies such as infrared, radio, and microwave are included in thedefinition of medium. It should be understood, however, thatcomputer-readable storage media and data storage media do not includeconnections, carrier waves, signals, or other transitory media, but areinstead directed to non-transitory, tangible storage media. Disk anddisc, as used herein, includes compact disc (CD), laser disc, opticaldisc, digital versatile disc (DVD), floppy disk and Blu-ray disc wheredisks usually reproduce data magnetically, while discs reproduce dataoptically with lasers. Combinations of the above should also be includedwithin the scope of computer-readable media.

Instructions may be executed by one or more processors, such as one ormore digital signal processors (DSPs), general purpose microprocessors,application specific integrated circuits (ASICs), field programmablelogic arrays (FPGAs), or other equivalent integrated or discrete logiccircuitry. Accordingly, the term “processor,” as used herein may referto any of the foregoing structure or any other structure suitable forimplementation of the techniques described herein. In addition, in someaspects, the functionality described herein may be provided withindedicated hardware and/or software modules configured for encoding anddecoding, or incorporated in a combined codec. Also, the techniquescould be fully implemented in one or more circuits or logic elements.

The techniques of this disclosure may be implemented in a wide varietyof devices or apparatuses, including a wireless handset, an integratedcircuit (IC) or a set of ICs (e.g., a chip set). Various components,modules, or units are described in this disclosure to emphasizefunctional aspects of devices configured to perform the disclosedtechniques, but do not necessarily require realization by differenthardware units. Rather, as described above, various units may becombined in a codec hardware unit or provided by a collection ofinteroperative hardware units, including one or more processors asdescribed above, in conjunction with suitable software and/or firmware.

Various examples have been described. These and other examples arewithin the scope of the following claims.

What is claimed is:
 1. A method of processing media data, the methodcomprising: parsing, by a processor implemented in circuitry, abitstream including data formatted according to Common Media ApplicationFormat (CMAF); detecting, by the processor and during the parsing, afile type (FTYP) value for a CMAF track file of the bitstream;determining, by the processor, that a CMAF header of the CMAF track filestarts with the FTYP value; and processing, by the processor, one ormore CMAF fragments following the CMAF header of the CMAF track file,wherein processing the one or more CMAF fragments comprises: detectingone or more segment type (STYP) values in the bitstream; determiningthat each of the one or more STYP values corresponds to a start of arespective one of the CMAF fragments; determining that at least one ofthe STYP values comprises “cmff;” and processing each of the CMAFfragments starting from the corresponding STYP value, comprising, inresponse to determining that the at least one of the STYP valuescomprises “cmff,” processing data of the bitstream immediately followingthe at least one of the STYP values as corresponding to samples of thecorresponding one of the CMAF fragments.
 2. The method of claim 1,further comprising: determining that at least one of the STYP values fora corresponding one of the CMAF fragments has a value indicating thatthe corresponding one of the CMAF fragments includes a CMAF chunk; andprocessing the CMAF chunk in response to determining that the at leastone of the STYP values has the value indicating that the correspondingone of the CMAF fragments includes the CMAF chunk.
 3. The method ofclaim 2, wherein the value for the at least one of the STYP valuescomprises “cmfl”.
 4. The method of claim 1, further comprising:determining that at least one of the STYP values for a corresponding oneof the CMAF fragments has a value indicating that the corresponding oneof the CMAF fragments is included in a CMAF segment of the CMAF trackfile; and processing the CMAF segment in response to determining thatthe at least one of the STYP values has the value indicating that thecorresponding one of the CMAF fragments is included in the CMAF segment.5. The method of claim 4, wherein the value for the at least one of theSTYP values comprises “cmfs”.
 6. The method of claim 4, whereinprocessing the CMAF segment comprises processing one or more CMAFfragments included in the CMAF segment.
 7. The method of claim 1,wherein processing the one or more CMAF fragments comprises determiningthat data following the CMAF header represents the one or more CMAFfragments in response to detection of the FTYP value.
 8. A device forprocessing media data, the device comprising: a memory for storing mediadata; and one or more processors implemented in circuitry and configuredto: parse a bitstream including the media data, the bitstream beingformatted according to Common Media Application Format (CMAF); detect,during the parsing, a file type (FTYP) value for a CMAF track file ofthe bitstream; determine that a CMAF header of the CMAF track filestarts with the FTYP value; and process one or more CMAF fragmentsfollowing the CMAF header of the CMAF track file, wherein to process theone or more CMAF fragments, the one or more processors are configuredto: detect one or more segment type (STYP) values in the bitstream;determine that each of the one or more STYP values corresponds to astart of a respective one of the CMAF fragments; determine that at leastone of the STYP values comprises “cmff,” and process each of the CMAFfragments starting from the corresponding STYP value, wherein the one ormore processors are further configured to, in response to determiningthat the at least one of the STYP values comprises “cmff,” process dataof the bitstream immediately following the at least one of the STYPvalues as corresponding to samples of the corresponding one of the CMAFfragments.
 9. The device of claim 8, wherein the one or more processorsare further configured to: determine that at least one of the STYPvalues for a corresponding one of the CMAF fragments has a valueindicating that the corresponding one of the CMAF fragments includes aCMAF chunk; and process the CMAF chunk in response to determining thatthe at least one of the STYP values has the value indicating that thecorresponding one of the CMAF fragments includes the CMAF chunk.
 10. Thedevice of claim 9, wherein the value for the at least one of the STYPvalues comprises “cmfl”.
 11. The device of claim 8, wherein the one ormore processors are further configured to: determine that at least oneof the STYP values for a corresponding one of the CMAF fragments has avalue indicating that the corresponding one of the CMAF fragments isincluded in a CMAF segment of the CMAF track file; and process the CMAFsegment in response to determining that the at least one of the STYPvalues has the value indicating that the corresponding one of the CMAFfragments is included in the CMAF segment.
 12. The device of claim 11,wherein the value for the at least one of the STYP values comprises“cmfs”.
 13. The device of claim 11, wherein the one or more processorsare configured to process one or more CMAF fragments included in theCMAF segment.
 14. The device of claim 8, wherein the one or moreprocessors are configured to determine that data following the CMAFheader represents the one or more CMAF fragments in response todetection of the FTYP value.
 15. A device for processing media data, thedevice comprising: means for parsing a bitstream including dataformatted according to Common Media Application Format (CMAF); means fordetecting, during the parsing, a file type (FTYP) value for a CMAF trackfile of the bitstream; means for determining that a CMAF header of theCMAF track file starts with the FTYP value; and means for processing oneor more CMAF fragments following the CMAF header of the CMAF track file,wherein the means for processing the one or more CMAF fragmentscomprises: means for detecting one or more segment type (STYP) values inthe bitstream; means for determining that each of the one or more STYPvalues corresponds to a start of a respective one of the CMAF fragments;means for determining that at least one of the STYP values comprises“cmff,” and means for processing each of the CMAF fragments startingfrom the corresponding STYP value, the means for processing each of theCMAF fragments starting from the corresponding STYP value comprisingmeans for processing, in response to determining that the at least oneof the STYP values comprises “cmff,” data of the bitstream immediatelyfollowing the at least one of the STYP values as corresponding tosamples of the corresponding one of the CMAF fragments.
 16. The deviceof claim 15, wherein the samples of the CMAF fragments comprise samplesof first CMAF fragments, and wherein the means for processing each ofthe CMAF fragments further comprises: means for processing second CMAFfragments of the one or more CMAF fragments as being included inrespective CMAF segments when corresponding STYP values for the secondCMAF fragments have a value of “cmfs;” and means for processing thirdCMAF fragments of the one or more CMAF fragments as including respectiveCMAF chunks when corresponding STYP values for the third CMAF fragmentshave a value of “cmfl”.
 17. A computer-readable storage medium havingstored thereon instructions that, when executed, cause a processor to:parse a bitstream including data formatted according to Common MediaApplication Format (CMAF); detect, during the parsing, a file type(FTYP) value for a CMAF track file of the bitstream; determine that aCMAF header of the CMAF track file starts with the FTYP value; andprocess one or more CMAF fragments following the CMAF header of the CMAFtrack file, wherein the instructions that cause the processor to processthe one or more CMAF fragments comprise instructions that cause theprocessor to: detect one or more segment type (STYP) values in thebitstream; determine that each of the one or more STYP valuescorresponds to a start of a respective one of the CMAF fragments;determine that at least one of the STYP values comprises “cmff,” andprocess each of the CMAF fragments starting from the corresponding STYPvalue, wherein the instructions that cause the processor to process eachof the CMAF fragments starting from the corresponding STYP valuecomprise instructions that cause the processor to process data of thebitstream immediately following the at least one of the STYP values ascorresponding to samples of the corresponding one of the CMAF fragments.18. The computer-readable storage medium of claim 17, wherein thesamples of the CMAF fragments comprise samples of first CMAF fragments,and wherein the instructions that cause the processor to process each ofthe CMAF fragments further comprise instructions that cause theprocessor to: process second CMAF fragments of the one or more CMAFfragments as being included in respective CMAF segments whencorresponding STYP values for the second CMAF fragments have a value of“cmfs;” and process third CMAF fragments of the one or more CMAFfragments as including respective CMAF chunks when corresponding STYPvalues for the third CMAF fragments have a value of “cmfl”.